KR20140099253A - A prosthesis - Google Patents

Abstract

The prosthesis (2) comprises: a first part (4) formed of a fiber-reinforced polymer material and having a bearing surface; And a second component (6) configured to articulate with a bearing surface of the first component (4), wherein at least a portion of the bearing surface of the second component (6) is surface treated to form an abrasion resistant surface.

Description

Prostheses {A PROSTHESIS}

The present invention relates to prostheses, and more particularly to hip resurfacing prosthesis non-exclusively.

It is known to replace some or all of the damaged or diseased natural bone joint with a prosthetic component. For example, a degenerated hip joint may be replaced by an artificial joint comprising a prosthetic acetabular cup component implanted into a patient's acetabulum, and a prosthetic femoral component implanted into the patient's femur and connected to the acetabular cup . This type of prosthetic joint is known as total hip replacement. Alternatively, a hip replacement procedure in which a cap is placed on an existing femoral head may be used. This cap is articulated to the acetabular cup in much the same way as in total hip arthroplasty. However, since the existing femoral head is preserved in the surface replacement process, the bone is hardly removed compared to the total hip replacement.

Conventional means of securing an acetabular cup are to additionally use bone cement as needed to bring the cup into close contact with the prepared acetabulum. This is acceptable in many cases, but is not an option for patients who have degenerated much of acetabular bone. Additional fixation may be provided by bone screws passing through the cup and deeply engaging the patient's bone tissue to keep the cup in place. Generally, a liner is fitted over the screw head over this cup to provide the articulating surface of the femoral head. GB0815884.2 discloses a carbon fiber reinforced polyether ether ketone (CFR) containing an opening to allow the cup to pass through the acetabulum by passing a screw or the like (formed of carbon fiber-reinforced polyetheretherketone (CFR-PEEK) -PEEK). ≪ / RTI > CFR-PEEK operates under boundary lubrication and does not affect the abrasion performance of the bearing surface in the presence of an opening.

However, there have been studies suggesting that carbon fibers in the CFR-PEEK material can scratch the surface of the femoral head component. This can accelerate the frictional wear of the acetabular cup. Thus, it is desirable to form the femoral head component with a ceramic material that resists scratches by carbon fibers. Nonetheless, making femoral head parts with ceramics is technically more challenging than metal parts. Further, in the surface substitution process, the ceramic surface replacement component may need to be thicker than the corresponding metal component. As a result, ceramic components may require the removal of potentially more bone than is required in metal surface replacement parts.

The present invention seeks to solve some or all of the problems described above.

According to an aspect of the present invention there is provided a first component formed from a fiber-reinforced polymer material and having a bearing surface; And a second component configured to be articulated with the bearing surface of the first component, wherein at least a portion of the bearing surface of the second component is surface treated to form a scratch or abrasion resistant surface.

The abrasion resistant coating can prevent the bearing surface of the second component from being scratched by the fibers in the fiber reinforced polymeric material. Without this wear-resistant coating, friction wear of the first component can be accelerated. Thus, this wear resistant coating can improve the durability of the prosthesis.

The first part may be formed of carbon fiber reinforced polyetheretherketone (CFR-PEEK).

The surface treatment may include a hardening treatment such as a diffusion hardening treatment.

The surface treatment may comprise a wear resistant coating applied to the bearing surface.

The coating may be a superlattice coating.

The coating may comprise a ceramic material.

The second component may be formed of a metallic material.

The second component may be formed of a cobalt chromium alloy.

The abrasion resistant coating may seal the metal of the second component from the articular interface to prevent metal ion release.

The prosthesis may be a hip prosthesis, the first part may include an acetabular cup, and the second part may include a femoral head component.

The acetabular cup may be a monoblock (i.e., of a single piece) cup.

The femoral head part may be a surface replacement part.

The abrasion resistant coating does not add significantly to the thickness of the second part, thereby allowing the thickness of the second part to remain at a minimum. As a result, the amount of bone to be removed can be reduced. Thus, the present invention may be particularly suitable for the surface substitution process.

The bearing surface of the first component may include one or more bores for receiving one or more attachment means for securing the first component in place.

The fiber reinforced polymer may operate under boundary lubrication, so that the presence of the bore may not affect the wear performance of the bearing surface.

Further, through the bore, the surgeon can determine whether the first part is correctly positioned.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the present invention and the manner in which it may be practiced, reference will now be made, by way of example, to the accompanying drawings.
1 is an exploded side view of a prosthesis according to an embodiment of the present invention;

Referring to FIG. 1, a prosthesis 2 according to an embodiment of the present invention includes an acetabular cup 4 and a femur surface replacement part 6.

The acetabular cup (4) is a monoblock component formed of a fiber-reinforced polymer such as carbon fiber-reinforced polyetheretherketone (CFR-PEEK). The acetabular cup 4 is generally hemispherical and defines an inner surface (not shown) and an outer surface 8.

In use, the inner surface forms the bearing surface and the outer surface 8 contacts the appropriately widened acetabulum of the patient, as described in more detail below. The outer surface 8 of the acetabular cup 4 may be provided with a closed pore porous coating and / or a hydroxyapatite (HA) coating to support fixation through osseointegration. Alternatively, the outer surface 8 may comprise a porous titanium bone ingrowth surface having interconnected pores. The outer surface 8 of the acetabular cup 4 may have a diameter of 44 to 66 mm. This diameter can be chosen to provide an exact anatomical fit with the patient's acetabulum.

The acetabular cup 4 includes a plurality of bores (not shown). The bore may extend from the outer surface 8 to the inner surface through the acetabular cup 2. Alternatively, the bore may be a blind bore extending only partially from the outer surface 8 to the acetabular cup 2. [ The bore accommodates fastening means 10 such as screws, pins, barbs, spikes or any other suitable fastening device. The fastening means 10 may be used to improve fixation of the acetabular cup 2 to the acetabulum of the patient.

As described above, the CFR-PEEK operates under boundary lubrication so that the presence of the bore does not affect the wear performance of the bearing surface.

The femur surface replacement component 6 is formed of a metallic material, such as a cobalt chromium alloy, and includes a spherical cap portion 12 and a central post 14 extending from the inner surface of the spherical cap portion 12.

The spherical cap portion 12 and the inner surface of the post 14 may be grit blasted to provide a rough surface that supports the integration of the patient's bone and femoral surface replacement component 6 have.

The spherical cap portion 12 may be a diameter of 38 to 60 mm and is selected to have a complementary complement to the inner bearing surface of the acetabular cup 4. [ The thickness of the spherical cap portion 12 is minimized to reduce the amount of bone removed from the femoral head.

The post 14 is cylindrical and may have a uniform cross-section along its length. This can deliver uniform stress across the femoral head. Furthermore, grooves are formed in the posts 14 to provide rotational stability.

The outer surface 16 of the spherical cap portion 12 forms a bearing surface, and the outer surface 16 is provided with a wear resistant coating. The abrasion resistant coating may be a superlattice coating, especially a superlattice coating comprising a ceramic material. However, other types of wear resistant coatings may be used.

The patient's acetabulum and femoral head are widened before the prosthesis is implanted. The acetabular cup (4) is in close contact with the prepared acetabulum and the femoral surface replacement component (6) is cemented to the prepared femoral head. The joint is reduced and then the spherical cap portion 12 of the femur surface replacement component 6 is received in the inner surface of the acetabular cup 4. [

The spherical cap portion 12 through the abrasion resistant coating on the outer surface 16 of the spherical cap portion 12 is supported by the carbon fibers of the CFR-PEEK material during the articulation of the acetabular cup 4 and the femur surface replacement component 6 Scratching is prevented. Otherwise, scratches can accelerate the frictional wear of the acetabular cup 4. [ Thus, the wear resistant coating improves the durability of the prosthesis 2.

Further, the abrasion resistant coating does not add significantly to the thickness of the spherical cap portion 12, so that the thickness of the spherical cap portion 12 can be kept at a minimum. As a result, the femur surface replacement component 6 of the present invention reduces the amount of bone to be removed from the femoral head compared to ceramic components.

Moreover, the abrasion resistant coating seals the metal of the spherical cap portion 12 from the joint interface to prevent metal ion release (i.e., cobalt and chromium ions). Such metal ion release is undesirable because it can cause effects such as induction reactions, physiological tumors, and genotoxicity.

The present invention thus allows the CFR-PEEK to be used to form the acetabular cup 4. This is desirable because CFR-PEEK allows additional fixing means to be used, as described above. This is not possible in metal monoblock cups. Further, through the bore passing through the acetabular cup 4, the surgeon can determine whether the acetabular cup 4 is fully seated after it is attached. CFR-PEEK cups are considered more tolerant than hard-on-hard bearings in the situation where this cup is placed vertically.

Although the present invention has been described with respect to hip joint surface replacement prostheses, the present invention can be applied to other types of prostheses. For example, the present invention may be applied to a total hip replacement prosthesis, or to other anatomical joint prostheses such as knees or shoulders.

Other types of surface treatment may be performed on the outer surface 16 of the spherical cap portion 12 to form a scratch or abrasion resistant surface. For example, the outer surface 16 may undergo a curing process such as diffusion hardening. The curing treatment may be used in place of the abrasion-resistant coating described above, or may be used in addition to the abrasion-resistant coating to form a duplex treatment.

Claims (14)

As a prosthesis,
A first component formed from a fiber reinforced polymeric material and having a bearing surface; And
And a second component configured to be articulated to the bearing surface of the first component, wherein at least a portion of the bearing surface of the second component is surface treated to form an abrasion resistant surface. The prosthesis according to claim 1, wherein the first part is formed of carbon fiber-reinforced polyetheretherketone (CFR-PEEK). The prosthesis according to claim 1 or 2, wherein the surface treatment includes a hardening treatment. The prosthesis according to claim 3, wherein the curing treatment is a diffusion hardening treatment. 5. Prosthesis according to any one of claims 1 to 4, characterized in that the surface treatment comprises a wear resistant coating applied to the bearing surface. 6. The prosthesis according to claim 5, wherein the coating is a superlattice coating. 7. Prosthesis according to any one of claims 1 to 6, characterized in that the coating comprises a ceramic material. The prosthesis according to any one of claims 1 to 7, wherein the second part is formed of a metallic material. The prosthesis according to claim 8, wherein the second part is formed of a cobalt chromium alloy. 10. Prosthesis according to any one of claims 1 to 9, characterized in that the prosthesis is a hip prosthesis, the first part comprises an acetabular cup and the second part comprises a femoral head part. 11. The prosthesis according to claim 10, wherein the acetabular cup is a monoblock cup. The prosthesis according to claim 10 or 11, wherein the femoral head part is a surface replacement part. 13. Prostheses according to any one of the preceding claims, characterized in that the bearing surface of the first part comprises one or more bores for receiving one or more attachment means for securing the first part in place . Prostheses as shown in the accompanying drawings and as substantially described herein.

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